Feasibility of Using PZT Actuators to Study the Dynamic Behavior of a Rotating Disk due to Rotor-Stator Interaction

Presas, Alexandre; Egusquiza, Eduard; Valero, Carme; Valentín, David; Seidel, U.

doi:10.3390/s140711919

Cited by 33 publications

(33 citation statements)

References 24 publications

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“…This system is mounted at the tip of the shaft. This test rig has been used in previous studies to analyze the dynamic behavior of the submerged disk-like structures [26,28,29,[33][34][35].…”

Section: Test Rig Descriptionmentioning

confidence: 99%

“…The test rig consists of a rotating disk submerged and confined in water. The disk has been instrumented with a PZT (piezoelectric patch) [26][27][28][29][30] and different sensors (accelerometers, AE, and a microphone) have been located in the rotating and stationary parts of the test rig. In that way, the transmission of different excitation patterns simulating cavitation to the different parts of the test rig can be studied in detail.…”

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confidence: 99%

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Transmission of High Frequency Vibrations in Rotating Systems. Application to Cavitation Detection in Hydraulic Turbines

et al. 2018

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Abstract:One of the main causes of damage in hydraulic turbines is cavitation. While not all cavitation appearing in a turbine is of a destructive type, erosive cavitation can severely affect the structure, thus increasing maintenance costs and reducing the remaining useful life of the machine. Of all types of cavitation, the maximum erosion occurs when clouds of bubbles collapse on the runner surface (cloud cavitation). When this occurs it is associated with a substantial increase in noise, and vibrations that are propagated everywhere throughout the machine. The generation of these cavitation clouds may occur naturally or it may be the response to a periodic pressure fluctuation, like the rotor/stator interaction in a hydraulic turbine. Erosive bubble cavitation generates high-frequency vibrations that are modulated by the shedding frequency. Therefore, the methods for the detection of erosive cavitation in hydraulic turbines are based on the measurement and demodulation of high-frequency vibrations. In this paper, the feasibility of detecting erosive cavitation in hydraulic turbines is investigated experimentally in a rotating disk system, which represents a simplified hydraulic turbine structure. The test rig used consists of a rotating disk submerged in a tank of water and confined with nearby axial and radial rigid surfaces. The excitation patterns produced by cloud cavitation are reproduced with a PZT (piezoelectric patch) located on the disk. These patterns include pseudo-random excitations of different frequency bands modulated by one low carrier frequency, which model the erosive cavitation characteristics. Different types of sensors have been placed in the stationary and in the rotating parts (accelerometers, acoustic emission (AE), and a microphone) in order to detect the excitation pattern. The results obtained for all the sensors tested have been compared in detail for the different excitation patterns applied to the disk. With this information, the best location and type of sensor to detect the different excitations have been identified. This study permits improving the actual technique of detecting erosive cavitation in hydraulic turbines and, therefore, to avoid operation under these circumstances.

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Section: Test Rig Descriptionmentioning

confidence: 99%

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confidence: 99%

Transmission of High Frequency Vibrations in Rotating Systems. Application to Cavitation Detection in Hydraulic Turbines

et al. 2018

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“…[6][7][8][9] However, this method is unsuitable for applications where position or velocity sensors such as an encoder cannot be attached to objects. Several applications include blades used for wind power generation, automobile tires, and the wobbling drum of washing machines.…”

Section: Introductionmentioning

confidence: 99%

Image-based tracking system for rotating object vibration measurement using laser scanning vibrometer

Kim

Khalil

Nam

et al. 2015

Int. J. Precis. Eng. Manuf.

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An image-based tracking system using a laser scanning vibrometer is developed for vibration measurement of a rotating object in order to take advantage of rotation tracking without attaching an external sensor such as an encoder to the object. An image processing algorithm is used to detect a landmark and laser beam and track all vibration measuring points on a rotating object. To verify the performance of the proposed tracking system, processing time analysis of the image processing algorithm is carried out. The accuracy of the tracking system is also experimentally tested. Finally, the experimental results of modal analysis of the object without and with rotation are compared and the vibration measurement of the object is validated.

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“…The amplitude of this excitation depends on several parameters being the most important ones the combination of runner blades and guide vanes, the radial gap between runner blades/guide vanes, the blade load, and the hydraulic system response. The dynamic response of the runner is affected by the added mass and by the radial and axial gaps size [26][27][28][29][30][31]. Vibrations generated depend on the excitation forces and on the dynamic response of the runner, thus they are much affected by these gaps.…”

Section: Analysis Of Vibration Signaturesmentioning

confidence: 99%

Extension of Operating Range in Pump-Turbines. Influence of Head and Load

Valero

Egusquiza

et al. 2017

Energies

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Due to the increasing share of new renewable energies like wind and solar in the generation of electricity the need for power regulation and energy storage is becoming of paramount importance. One of the systems to store huge amounts of energy is pumped storage using reversible hydropower units. The machines used in these power plants are pump-turbines, which can operate as a pump and as a turbine. The surplus of electrical energy during low consumption hours can be converted into potential hydraulic energy by pumping water to a higher level. The stored energy can be converted into electricity again by operating the runner as a turbine. Due to new regulation requirements machines have to extend the operating range in order to match energy generation with consumption for the grid stability. In this paper the consequences of extending the operating range in existing pump-turbines have been studied. For that purpose, the data obtained after two years of condition monitoring were analyzed. Vibrations and pressure fluctuations of two pump-turbines of 85 MW each have been studied during pump and turbine operation. For turbine operation the effects of extending the operating range from the standard range of 45-85 MW to and increased range of 20-85 MW were analyzed. The change in vibration levels and signatures at very low load are presented with the identification of the phenomena that occur under these conditions. The influence of head in the vibration behavior is also presented. The appearance of fluid instabilities generated at part load that may produce power swing is also presented. Finally, the effect of head on the vibration levels for pump operation is shown and analyzed.

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Feasibility of Using PZT Actuators to Study the Dynamic Behavior of a Rotating Disk due to Rotor-Stator Interaction

Cited by 33 publications

References 24 publications

Transmission of High Frequency Vibrations in Rotating Systems. Application to Cavitation Detection in Hydraulic Turbines

Transmission of High Frequency Vibrations in Rotating Systems. Application to Cavitation Detection in Hydraulic Turbines

Image-based tracking system for rotating object vibration measurement using laser scanning vibrometer

Extension of Operating Range in Pump-Turbines. Influence of Head and Load

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